cvs commit: src/sys/amd64/include vmparam.h src/sys/arm/include vmparam.h src/sys/i386/include vmparam.h src/sys/ia64/include vmparam.h src/sys/kern kern_exec.c vfs_bio.c src/sys/powerpc/include vmparam.h src/sys/sparc64/include ...

[Alan Cox]

alc         2007-09-25 06:25:07 UTC

  FreeBSD src repository

  Modified files:
    sys/amd64/include    vmparam.h 
    sys/arm/include      vmparam.h 
    sys/i386/include     vmparam.h 
    sys/ia64/include     vmparam.h 
    sys/kern             kern_exec.c vfs_bio.c 
    sys/powerpc/include  vmparam.h 
    sys/sparc64/include  vmparam.h 
    sys/sun4v/include    vmparam.h 
    sys/sys              vmmeter.h 
    sys/vm               vm_contig.c vm_fault.c vm_map.c 
                         vm_object.c vm_object.h vm_page.c 
                         vm_page.h vm_pageout.c vm_pageq.c 
                         vm_phys.c vm_phys.h 
  Log:
  Change the management of cached pages (PQ_CACHE) in two fundamental
  ways:
  
  (1) Cached pages are no longer kept in the object's resident page
  splay tree and memq.  Instead, they are kept in a separate per-object
  splay tree of cached pages.  However, access to this new per-object
  splay tree is synchronized by the _free_ page queues lock, not to be
  confused with the heavily contended page queues lock.  Consequently, a
  cached page can be reclaimed by vm_page_alloc(9) without acquiring the
  object's lock or the page queues lock.
  
  This solves a problem independently reported by tegge@ and Isilon.
  Specifically, they observed the page daemon consuming a great deal of
  CPU time because of pages bouncing back and forth between the cache
  queue (PQ_CACHE) and the inactive queue (PQ_INACTIVE).  The source of
  this problem turned out to be a deadlock avoidance strategy employed
  when selecting a cached page to reclaim in vm_page_select_cache().
  However, the root cause was really that reclaiming a cached page
  required the acquisition of an object lock while the page queues lock
  was already held.  Thus, this change addresses the problem at its
  root, by eliminating the need to acquire the object's lock.
  
  Moreover, keeping cached pages in the object's primary splay tree and
  memq was, in effect, optimizing for the uncommon case.  Cached pages
  are reclaimed far, far more often than they are reactivated.  Instead,
  this change makes reclamation cheaper, especially in terms of
  synchronization overhead, and reactivation more expensive, because
  reactivated pages will have to be reentered into the object's primary
  splay tree and memq.
  
  (2) Cached pages are now stored alongside free pages in the physical
  memory allocator's buddy queues, increasing the likelihood that large
  allocations of contiguous physical memory (i.e., superpages) will
  succeed.
  
  Finally, as a result of this change long-standing restrictions on when
  and where a cached page can be reclaimed and returned by
  vm_page_alloc(9) are eliminated.  Specifically, calls to
  vm_page_alloc(9) specifying VM_ALLOC_INTERRUPT can now reclaim and
  return a formerly cached page.  Consequently, a call to malloc(9)
  specifying M_NOWAIT is less likely to fail.
  
  Discussed with: many over the course of the summer, including jeff@,
     Justin Husted @ Isilon, peter@, tegge@
  Tested by: an earlier version by kris@
  Approved by: re (kensmith)
  
  Revision  Changes    Path
  1.49      +3 -2      src/sys/amd64/include/vmparam.h
  1.11      +3 -2      src/sys/arm/include/vmparam.h
  1.45      +3 -2      src/sys/i386/include/vmparam.h
  1.17      +3 -2      src/sys/ia64/include/vmparam.h
  1.308     +1 -1      src/sys/kern/kern_exec.c
  1.527     +4 -10     src/sys/kern/vfs_bio.c
  1.10      +3 -2      src/sys/powerpc/include/vmparam.h
  1.18      +3 -2      src/sys/sparc64/include/vmparam.h
  1.5       +3 -2      src/sys/sun4v/include/vmparam.h
  1.34      +2 -2      src/sys/sys/vmmeter.h
  1.63      +2 -11     src/sys/vm/vm_contig.c
  1.236     +8 -21     src/sys/vm/vm_fault.c
  1.388     +7 -11     src/sys/vm/vm_map.c
  1.383     +30 -14    src/sys/vm/vm_object.c
  1.114     +1 -0      src/sys/vm/vm_object.h
  1.354     +271 -86   src/sys/vm/vm_page.c
  1.151     +11 -15    src/sys/vm/vm_page.h
  1.292     +2 -35     src/sys/vm/vm_pageout.c
  1.35      +0 -27     src/sys/vm/vm_pageq.c
  1.4       +115 -33   src/sys/vm/vm_phys.c
  1.3       +3 -0      src/sys/vm/vm_phys.h